Mandukya upanishad is a very short upanishad. Goudapada created a Kaarika for it. Sankaracharya did a Bhashya for the Karika. The experiences of us do not belong to the jagrad(awakened) state alone but also to drea, dreamless and even coma,trance states of existence. Consciousness studies have to encompass all these fields . Thus the upanishad takes us to the field of neurosciences and neurophysical studies of consciousness.